Document EP-A-1 279 591 in the name of the Applicant illustrates landing gear of the above-specified type. Reference can also be made, for technological background, to document U.S. Pat. No. 3,653,682 which illustrates a device for absorbing energy comprising two superposed shock absorbers.
In certain situations, when the aircraft is stationary or taxiing slowly on the ground, it is desirable to be able to modify the attitude of the aircraft, i.e. the angle of inclination of its longitudinal axis and/or of its transverse axis.
In document U.S. Pat. No. 5,310,140 in the name of the Applicant, an approach is described which consists in modifying the length of the nosegear without altering the main landing gear. The structure of the shock absorber described in that document makes it easy to lengthen the landing gear when the aircraft is stationary or taxiing slowly, without requiring the hydraulic generator of the aircraft to be used, i.e. without requiring its engines to be in operation.
Document U.S. Pat. No. 5,310,139 in the name of the Applicant also shows a nosegear shock absorber designed to perform the same function.
The present invention relates more specifically to the shock absorbers fitted to wide-body aircraft main landing gear of the type that is retracted vertically, comprising a plurality of independent legs arranged one behind another to form, in the landing gear down position, a row that is parallel to the longitudinal plane of the airplane, with a pair of wheels being mounted at the end of each leg. Such retractable landing gear for wide-body aircraft is described, for example, in document EP-A-0 676 328 and EP-A-0 614 804 in the name of the Applicant.
In other situations, it is desired to shorten or lengthen one or more legs when the aircraft is stationary or taxiing slowly. Such shortening or lengthening can be advantageous not only when it is desired to modify the attitude of the aircraft while stationary, in particular while loading said aircraft, but also in other particular situations such as when changing a tire or when unloading the front leg in order to facilitate steering maneuvers. For tire changing, it is conventional to use jack systems for lifting the structure of the aircraft in order to lift the tire for replacement out of contact with the ground.